It is critically important from the operation of cranes for lifting heavy loads that the operator of the crane have the capability of accurately identifying the actual weight of the load being lifted, including the load of various lifting components of the crane such as empty blocks, boom, etc. and for determining the percentage of the load being lifted in comparison with the maximum load for which the crane mechanism is designed.
In the past gantry cranes and other heavy lifting cranes have been provided with electronic load detection apparatus with the load cell being coupled in series with the deadline of the main hoist so that the load on the lines of the main hoist are measured directly and the angle of the boom is easily ascertained. These load cells, being located at or near the free end of the boom, are easily damaged by impacts caused by swinging of the main hoist block.